Problem: Solve for $y$ : $y - 3 = -20$
Explanation: Add $3$ to both sides: $ \begin{eqnarray} \\ y - 3 &=& -20 \\ \\ {+3} && {+3} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-3 + y} &\hphantom{=}& \hphantom{-20} \\ y &=& -20 {+ 3} \\ \end{eqnarray} $ Simplify. $ y = -17$